Method of cleaning metallic sheets



April 30, 1935. H. w. NIEMAN METHOD OF CLEANING METALLIC SHEETS FiledAug. 15, 1931 Patented Apr. 30, 1935 METHOD OF CLEANING METALLIC SHEETSHenry W. Nieman, Bethlehem, Pa", assignor to Bethlehem Steel Company, acorporation of Pennsylvania Application August 15,

3 Claims.

The present invention relates to methods of and apparatus for removingoil or oleaginous material from the surfaces of metalstrips or sheets.

Quite a large proportion'of the metallic sheets manufactured are,subsequent totheir fabrication, coated with tin. A satisfactory coatingof tin can only be applied toa sheet or strip having a clean surface,and hence it is essential that the sheets or strips which are passedinto the tinning machine be free of appreciable quantitles of oil and infact free of any liquid or solid matter which would tend to interfere inany way'with the tinning process.

Sheets are now rolled to finished gauge by two principal processesknown, respectively, as the hot rolling process and the cold rollingprocess. In the hot rolling process no oil is used, and hence the sheetscome from the mill with their surfaces in satisfactory condition. Inhandling these sheets, however, they frequently become coated with oil,at least in spots, and hence it is necessary 'under such conditions toremove the oil or greasy matter. very extensively in connection with thecold rolling process so that the sheets, as they come from the coldrolling mill, are generally quite oily or greasy.

The common practice now followed in preparing cold rolled sheets fortinning is to first anneal them and to thereafter pickle the an-.

nealed sheets prior to passing them through the tin pot. Prior tosubjecting the sheets to the action of the annealing furnace, however,it is essential that the oil be removed since, if it is not, theannealing operation causes the oil to form a film of graphite onthesurface of the sheet which resists the action of the pickling acids. Itis found that the usual methods of removing oil, which methods comprisewashing the metallic sheet in soda or other solution,

or mechanical cleaning as by bran cleaners, do

.not effect complete removal of the oily substances so that extremelythin films of oil remain when the sheets are introduced into theannealing furnace, and the resulting graphite seriously interferes withthe application of tin coating.

In accordance with the present invention, the cold rolled sheets withtheir oily or greasy surfaces, or the hot rolled sheet if such sheetshave become wholly or partially grease-coated in handling, are subjectedto a washing operation in a solvent which completely removes the coatingof oil thereon. This solvent is of such character that it may be eithercompletely removed Oil is used 1931, Serial No. 557,405

by mechanical means or, if not completely removed, will evaporatewithout leaving a graphite deposit on the sheet, so thatthe surface ofthe sheet is, after the annealing operation, in proper condition for theattack of pickling acids.

While various types of solvents may be used, I prefer to use kerosene asI have found this to work satisfactorily in practice and to berelatively inexpensive and easily handled. The term kerosene as hereinused designates that member of the series of petroleum distillateshaving a boiling point lower than that of the lubricating oils but notso low asto cause it to give off inflammable vapors at ordinarytemperatures. Other solvents of generally similar nature may beemployed, however, if found more suitable under varying operatingconditions.

The apparatus employed in cleaning the sheets or strips may vary widelyin detail, the invention not being limited in this respect. In theaccompanying drawing, two forms of such apparatus are illustrated by wayof example.

In the drawing:

Figure 1 illustrates diagrammatically a preferred form of apparatus; andI Figure 2 illustrates a diagrammatic showing of a modified form.

In the form of the apparatus shown in Figure 1, a tank for the liquidsolvent is indicated at It, this tank being open at the top and having acentral transverse partition H dividing the tank into two independentcompartments. The sheet or strip to be cleansed is mounted upon the druml2 and in-the cleansing operation is unwound from this drum and isultimately wound on a second drum [3 at the other end of the apparatus.

The sheet passes under a roller l4 in the first parallel manifolds 20,which manifolds are pro-f vided with apertures facing the sheet, throughwhich streams of solvent are discharged against the opposite sides ofthe sheet; A solvent outlet pipe is indicated at 2|, this pipe beingadapted to conduct solvent from the bottom of tank ID to the inlet sideof a pump 22. A pipe'or conduit 23 conducts solvent under pressure fromthe outlet side of pipe 22 to the manifolds 20.

In the operation of the device, the greater quantity of the oily matterof the surfaces of the sheet is removed by the solvent in the firstcompartment of the tank, and this solvent, which is preferably kerosene,may be removed, purified, and replaced from time to time as isnecessary. The solvent in the first compartment is prevented fromentering the second by reason of the rubberwipers l5. In passing throughthe second compartment, any traces of the oily material on the surfacesof the sheets which may still remain are removed, and the solvent isremoved from the surface of the sheet prior to the passage of the sheetto the tank by the rubber wiping devices l8. Any remaining traces ofsolvent are removed by the action of the bran cleaner I! of well-knownconstruction prior to the winding of the sheet on the drum IS.

The sheet thus treated may be readily subjected to the action of theannealing furnace, and, should any slight traces of solvent remain onits surface, this solvent will evaporate and not form graphite depositswhich tend to interfere with the action of the pickling bath.

The form of the apparatus shown in Figure 2 is similar in its action,but in this instance the tank 30 is divided into a number ofcompartments by partitions 3|. The compartments, however, communicatewith each other below the level of the solvent, the partitions 3| beingprovided with relatively small apertures 32 for this purpose. The sheet33 passes successively under rollers 34, one roller being located ineach compartment, and successively over the partitions 3| and is finally*removed, subjected to the action of the bran cleaner 35, and then woundupon a suitable drum. Rubber wiping devices are indicated at 36. A pipeor conduit 31 connects the two end compartments and, if the sheet ispassed through the tank in the direction of the arrow B, solvent isremoved from the first or entering compartment by the action of pump 40and introduced intothe last compartment, after first passing through asuitable purifying or distilling device 42 by means of which theimpurities may be removed. By constantly removing solvent from theentering compartment, purifying it, and returning it to the outgoingcompartment and inducing a flow of solventfrom one end of the tank tothe other in a direction opposite to that in which the sheet is passedthrough, efiiciency of cleansing action is promoted.

In adapting the invention to the treatment of sheets, strips, and thelike which vary in size, shape, and surface characteristics, the designand arrangement of the various elements of the solvent tank may bechanged considerably without departure from the teaching thereof. Theprecise composition of the solvent used may also be varied, whendesired, to insure maximum efiiciency of the process in treating allsizes and compositions of sheets and strips.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In the process of producing metallic sheet, the steps of cold rollinga sheet while applying lubricant thereto, washing said sheet inkerosene, and subjecting said sheet to an annealing temperature.

2. In the process of producing metallic sheet, the steps of cold rollingsaid sheet while applying lubricant thereto, washing said sheet inkerosene,

removing a portion of said kerosene from said sheet by mechanical means,removing a remaining portion of said kerosene from said sheet bysubjecting said sheet to an annealing treatment,

pickling said sheet and applying a coating of protecting metal to thesurface thereof.

3. In the process of producing tin plate, the steps of cold rollingsteel sheet material while applying lubricant thereto, washing saidmaterial in kerosene, removing adhering portions of said kerosene bysubjecting said material to an anhealing treatment, pickling saidmaterial and applying a coating of tin thereto.

HENRY W. NIEMAN.

